Electric control apparatus for fuel burners



May 12, 1936. LyM. PERSONS ELECTRIC CONTROL APPARATUS FOR FUEL BURNERS Filed Nov. 1'7, 1933 2 Sheets-Sheet l CURRENT SUPPLY May 12, 1936. L. M. PERSONS 2,040,402

ELECTRIC CONTROL APPARATUS FOR FUEL BURNERS Filed Nov. 17, 1933 2 Sheets-Sheet 2 the ignition circuit after, a time period and to open relay starting holding contacts. so that upon Patented May 12, 1936 ELECTRIC CONTROL APPARATUS FOR FUEL BURNERS I Lawrence M. Persons, Des Moines,

to Penn Electric Switch 00., Des

a corporation of Iowa Application November 17, 1933, Serial No. 698,478

4 Claims. (Cl. 158-28) One object of my invention is to provide control apparatus for the electric circuit of a fuel burner, which apparatus is comparatively simple to manufacture and also inexpensive.

Iowa, assignor Moines, Iowa,

them until a room thermostat is closed, these contacts being so mounted on a relay that they re- A further object'is to provide an automatic controller including a combustion switch which is opened when combustion occurs in order to break the circuit through a heater of a lock-out switch so that upon combustion occurring the lock-out switch will not thereafter lock out.

Still a further object is to provide control apparatus including a room thermostat operated relay which initiates and terminates operation of a fuel burner and which initiates operation of ignition mechanism for thefuel burner, tennination of the operation of the ignition mechanism being effected by'an ignition trip mechanism which in turn is operated by the heating of a warp switch when in ltshot position; a 'combustion switch being provided to cause'operation of the heater of the warp switch,

A further object is to provide control apparatus including a warp switch operating toa'terminate flame failure, a purging period is provided before .the control apparatus re-initiates operation of the fuel burner by re-engaging said relay starting ,holding contacts, thus allowing the combustion chamber to be cleared of dangerous gases by the natural draft in the furnace before the ignition mechanism is re-energized and thus eliminating an explosion upon such re-energization.

My control apparatus may be used in connection with a fuel burner for burning oil, gas or other fuel whereby upon combustion failure occurring such as caused by a down-draft in the furnace,- a slug of water in the fuel oil or the like, automatic operation of the controller will recycle after a purging period has been provided to allow the draft of the furnace to purge the combustion chamber of any explosive gas caused by the in troduction of fuel after combustion fails, or will, after several purging periods, stop the operation of the burner until the same hasbeen remedied and the apparatus reset.

main on when the relay is energized and ignition trip mechanism being provided for thereafter tripping them to the off position.

, Another object is to provide means for controlling the ignition trip mechanism from a confbustion switch, a delayed action mechanism being interposed between the combustion switch and the ignition trip mechanism so that ignition is had over a considerable period of time, this being especially desirable for the rotary types of oil burners requiring a long ignition period for insuring combustion. I

Another object is to provide novel controlling l5 mechanism includinga relay or the like and a latch means cooperating with parts operated by the armature of the relay to cause certain con.

' tacts to remain in their normally relay de-ener- Still another object is to provide in a control apparatus, a combustion switch which opens the ,initial circuit through a lookout switch heater and closes it through the entire coil of arelay,

the lookout switch heater being in circuit with only a part of said coil. Another object is to provide a control strubture in which ignition contacts are normally closed,

but the ignition current does not flow through switch.

gized position when the relay coil is energized but 0 which will move to their other position when the latch means'is released, providing the relay coil is still energized. v

. with these and other. objects in view myinvention consists in the -construction, arrangement and combination of the various parts of my device, whereby the objects contemplated are attained, as hereinafter morefully set forth, pointed out in my claims, and illustrated in the accompanying drawings, in which:

Figure 1 is an electrical diagrammatic view of an electric control apparatus for fuel burners embodying my invention.

Figures 2, 3 and 4 are diagrams of the combustion switch of Figure 1 in different successive positions between thecold and hot positions of the Figure 5 is a partial view of the relay switch of Figure 1 showing it in energized position.

Figure 6 is a portion of Figure 5 showing an ignition trip mechanism in tripped position. v

Figure 7 is a diagram of the warp switch of Figure 1 showing it in an intermediate position.

Figure 8 is a similar view showing it in hot position;-and

Figure 9 is a simplified diagrammatic view of the system.

My apparatus includes a combustion switch having a shaft ll rotated by a bimetal or other type. of temperature responsive element It and in turn rotating a notched disk I5 with the periphery of which a leaf spring operating arm I! of; the combustion switch coacts. The combustion switch, includes starting contacts I 0, running hold- 2 contacts I4. The combustion switch operates as disclosed in the Williams Patent No. 1,82'7,703, issue October 13, 1931.

Operating from the cold position of Figure 1 to the hot position of Figure 4, the contacts l2 are first engaged, as in Figure 2, the contacts I4 are thenalso engaged as in Figure 3 and lastly the contacts l8 are opened as in Figure 4. The com-.

- bustion switch when operating from hot to cold position will cause the contacts to successively assume the positions of Figures 4, 3, 2, and 1.

The relay switch of my apparatus includes ignition contacts I6, motor contacts [8 and 28, second ary holding contacts 22 and primary holding contacts 24,'all of which are controlled by an armature 19 adapted to be attracted from the normal position of Figure 1 to the energized position of Figure 5 by either one or both coils "and 28 of the relay.

ter prevention contacts a ing contacts 44 and opened by a cam 38, which in turn is held in its inoperative position by a bimetal latch 48.

The latch 48 is adapted to be warped to unlatching position by a look-out switch heater 42.

The warp switch of my apparatus comprises a bimetal element 58 for opening normally closed starting contacts 44, normally closed chatter prevention contacts 48 and closing normally open ignition trip contacts 48. A warp switch heater 52 is provided for warping the bimetal element 58 from its normal position of Figure 1 to its hot position of Figure 8.

The ignition mechanism of a fuel burner and the burner motor usually provided'for operating a blower are connected in circuit with the look-out switch and the relay switch through terminals L ,'I, and M. A transformer 9 has its primary connected through the lock-out switch and with a current supply terminal L The transformer has a secondary winding for supplying current through a room thermostat R. T. connected with terminals R and R to the warp switch heater 52, lock-out switch heater 42, I

relay coil 28-28 and ignition trip magnet 38. Practical operation The circuit connections with the various coils, heaters, contacts, etc. are all fully shown in- Figures 1 and 9. The parts are in normal or nonoperating position.

Starting circuit When the room thermostat R. T. closes becauseof lowering of the room temperature to a predetermined degree, a starting circuit is clos' d (see Figure 9) from one end of the transformer secondary through R. T. and wire a and the coil 28 .of the relay switch, through the look-out switch heater 42, through the wire a, bimetal 58 and chat- 46 and through the startstarting contacts I8 of the combustion switch and wire e to the other end of the transformer secondary. This'causes the armature l8 to be attracted whereupon its contacts I8, 28, 22 and 24 are closed and I6 are urged to open but are held then through wire dand the;

establishing closed orin their normal position by the ignition trip armature 32 (see Figure 5).

The closing of the contacts l8 and 28 establishes through wires f, g and it both the motor circuit and the ignition circuit from the line through the look-out switch contacts 36, the ignition contacts l6 being already closed, the motor circuit also includingwires i and a and the ignition circuit wires k and Z.

I Running circuit Energization of ondary holding contacts 22 so that the current from the room thermostat can flow through wire a and the entire relay coil 28-28, then through wire m and the contacts-22 and wire it and through the running holding contacts 12 of the combustion switch and then through the wire 6 if combusticnoccurs and the switch moves to the position of Figure 2.

This circuit is normally maintained until the room thermostat opens the circuit because of rise of the temperature in the room to a predetermined degree, or in case of a non-normal condition-such.as combustion failure occurring, the

combustion switch will return to the cold position of Figure 1, thus opening ingcontacts l2 and opening the relay coil circuit through wires a, m, n, and e.-

Warp switch circuit If combustion normally occurs, the warp switch heater initiating contacts I4 will close after the contacts i2 close as in Figure 3, thus the circuit from the room thermostat through wires 0 and p and the warp switch heater 52 and wire q and the combustion switch contacts l4 and I2 and wire e to the upper end of the secondary coil of the transformer.

The warp switch heater 52 will gradually warp the element 58 to ,the position of then to the position of Figure 8. In Figure 7, the starting contacts shunting the contacts 24 by wires d, r, and s are opened and so are the chatter prevention contacts 46. In Figure 8, the ignition trip contacts 48 are closed, this occurring a substantial time period after the running holding contacts l2 of the combustion switch Figure 7 .and'

the relay coil 28 closes the secthe running hold are closed and this period of time being provided for continued energization of the ignition to give it plenty of time totcause combustion.

Closing of the contacts 48 establishes a circuit from the room thermostat through wires 0 and t and the ignition trip magnet 38 and its contacts 32 and 34 and then through wires u and m and the contacts '22 wire it and contacts 12 to the upper end of the secondary coil of the transformer through wire e. Energization of the magnet 38 attracts the armature 32 from the position of Figure5 to the position of Figure 6 and in so doing, the contacts Hand 34 are separated so that current flows only momentarily through the magnet 38 and the switch blade 35 springs upwardly to separate the ignition contacts I6. This de-energizes the ignition mechanism.

It. combustion does not occur in 'the ordinary manner, the combustion switch will remain in the position of Figure 1 and current will conthrough the look-out switch heater 42, coming through the relay-coil 28 and passing through the contacts 48, 44 .and I8 and through wires a, b, c, d, and 6. After a time period, the latch 48 will release the cam 38 for opening the contacts 38 and thus shutting oi the the control apparatus until the trouble is remedied and the lock-out switch'manually reset.

In case of failure of combustion after it once occurs however, it is desirable to provide a purgingperiod during which gases in the furnace can be purged therefrom by the natural draft and then have the control-apparatus re-cycle for'attempting another start as for instance when there,

is a down draft through the furnace or a slug of water in the fuel oil, the burner may be able to operate normally after a purging period. If

more than two or three of these purging periods occur however, it would undoubtedly be due to some trouble that could not be remedied by a purging period, whereupon the successive heatings of the look-out switch heater 42 would trip the look-out switch.

For the purging period, the combustion switch switch heater 52. In the position of Figure 1,

the contacts I! open for thus opening the circuit through the relay and shutting down the operation of the burner motor.

The bimetal element will now slowly move from the position of Figure 8 to the position of Figure 1 due to de-energization of the heater 52 and provide, during the time of such movement, the desired purging period. At first, the contacts 48 will be separated so they will be in position for initial operation and then the contacts 46 will close so that they also will be in position for initial operation and the tension of the leaf spring between the contacts 44 and 46 will be imposed on the bimetal 50 to dampen any tend-' ency of it to vibrate.

When the contacts 44 then close theywill do so without chattering due to such tension and the purging period is ended and the starting circuit is re-established through wires a, b, c, d, and e, as already described. v

It will; be noted that the starting circuit is not re-established until both the. chatter reven-= tion contacts 46 and the starting contac '44 of the warp. switch are closed. ,The' progressive movement of the bimetal element 50 of the warp switch during the cooling period is not necessarily smooth andif the contacts 44 only were provided, there would be a possibility of chattering in the starting circuit when they were closed. with the contacts 46 in serieswi ththem however, the contacts 46 are first closed and then the contacts 44 (which shunt the normally open primary holding contacts '24 of the relay switch) are losed. immediately causing the contacts 24 to close because of energization of the starting coil 28 of the relay switch.

. The ignition trip contacts 48 for controlling the ignition trip magnet 30 may be dispensed with where only a short ignition period is requlred, such as disclosed in my copending app cation,'Serial No. 698,477, filed November 17, 1 33. In the present application, the contacts 48 areused and closed after a delayed period of time by the bimetal element 54 of the warp switch so that a long ignition period is obtained.

Especially in the rotarytypes of burners where initiation of combustion is slow, an extended ignition period as accomplished by my present circult is desirable.

- ing contacts which are closed when the thermal warp element is cold shunting said primary hold- With respect to the contacts i I and Ill, either of these can be dispensed with'because they are in series and control the motor. The two of them. are used merely .so that the jumper 39 can be used instead of a single set of contacts and pig- 5 tall connections. This does away with connections of this character which are not entirely satisfactory. I

Although I have shown the latch 32 associated in-a fuel burner control apparatus, it is obvious 10 c that thissame latch can be associated with any my claims, any modified forms ofstructure' or use of mechanical equivalents, which may be reasonably includedwithin their scope.

I claim as my invention:

1. In a control system for a fuel burner and its fuel feeding means, a control'circuit including an igniter, a motor controlling fuel eed, a multiple contact relay operable when energized to close contacts energizing said motor and igniter and to close primary and secondary holding contacts in series with the coil of said relay,

an electrically actuated thermal warp switch having contacts to permit a starting circuit to be established while they are open, a combustion switch having first contacts operable to establish a circuit through said secondary holding contacts and having second contacts toenergize said warp switch upon combustion occurring, whereupon after a-time period the contacts of the warp switch are opened and the relay coil is maintained energized through said secondary holding con- 15 tacts and sai first contacts, said combustion switch upon 0 mbustion failure de-energizin'g said warp switch by opening said second contacts and opens said circuit established by said first contacts and including said secondary holding con- 50 tacts whereby said relay-is de-energized and said warp switch, after providing a purging period while it is'cooling down and upon reclomng its contacts will re-establish the circuit around said primary holding contacts to cause re-cycling of 55 said control system.

- v '2. In a control system for a fuel burner and its fuel feeding m a control circuit including an igniter, a motor controlling fuel feed, a multiple contact relay operable when energized to close I contacts energizing said motor and igniter and to close holding contacts in series with the coil of said relay, anelectrically actuated thermal warp switch having contacts which are closed 'whenthethermalwarpelementiscoidandwhich whereupon after a time period the. contacts of] thewarp switch are opened and the relay coil is maintained energized through said secondary circuit including said first contacts. said combustion 76 reclosing its contacts will r-establish the circuit around said holding contacts to cause re-cycling of said control system.

3. In a control system for a fuel burner and its fuel feeding means, a control circuit including an igniter, a motor controlling fuel feed, a multiple contact relay operablewhen energized to close,

contacts energizing said motor and igniter and to urge contacts controlling energization of said igniter which are closed when said relay is deenergized, towards open position, an electrically operable latch mechanism holding said ignition contacts closed when de-energized, said relay also operable when energized to close holding contacts in series with the coil of said relay, an electrically actuated thermal warp switch having contacts which are closed when the thermal warp element is cold and which shunt said holding contacts to permit a starting circuit to be established while they are open, a combustion switch having first contacts operable to establish a secondary circuit throughsaid relay coil and having second contacts to energize said warp switch upon combustion occurring whereupon after a time period the contacts of the Warp switch are opened and the relay'coil is maintained energized through said secondary circuit including saidfirst con-' tacts, said combustion switch upon combustion failure de-energizing said warp switch by opening said second contacts and opening said secondary circuit established by said first contacts whereby said relay is de-energized, said warp switch, after providing a purging period while it is cooling down and upon reclosing its contacts will re-establish the circuit around said holding contacts to cause re-cycling of saidcontrol systern, said warp switch also having contacts which are closed upon said warp switch assuming its warped position, said last contacts controlling energization of said latch mechanism.

4. In a control system for a fuel burner and its fuel feeding means, a control circuit including an igniter, a motor controlling fuel feed, an electrically actuated safety switch in said control circuit, a multiple contact relay operable when energized to close contacts energizing said motor and igniter and to urge contacts controlling energize,- tion ofsaid igniter which are closed when said relay is de-energized, towards open position, an :electrically operable latch mechanism holding said ignition contacts closed when tie-energized, said relay also operable when energized to' close holding contacts in series with the coil of said relay, an electrically actuated warp switch having contacts which are closed when the thermal warp element is cold and which shunt said holding contacts to permit a starting circuit to be established while they are open, means in circuit with the coil of said relay to open said safety switch after a time period of energization of said means, a combustion switch having first contacts operable to establish a secondary circuit through said relay coil and having second contacts to ener-,

gize said warp switch upon combustion occurring whereupon after a time period, the contacts of the warp switch are opened and the relay coil is maintained energized through said secondary circuit including said first contacts, said combustion,

switch having third contacts in series with the coil of said relay and opened 'uponcombustio'n establishment to terminate energization of said means to open said safety switch, said combustion switch upon combustion failure, de-energizing said warp switch by opening said second contacts and opens said secondary circuit established by said first. contacts, whereby said relay is deenergized and said warp switch, provides a purging period while it is cooling down and upon reclosing its contacts will re-establish the circuit around said holding contacts and through said thirdcontacts to cause re-cycling of said control system, said warp switch also having contacts which are closed upon said warp switch assuml ingits warped position, said last contacts controlling energization of said latch mechanism. LAWRENCE M. PERSONS. 

